Method of mixing propellant com-



Willard M. St. John, Jr., Waco, Tex., assignor to Phillips PetroleumCompany, a corporation of Delaware No Drawing. Filed Nov. 27, 1957, Ser.No. 699,424 7 Claims. (Cl. 52-.5)

This invention relates to a new propellant composition. In a furtheraspect this invention relates to a method of mixing the components of apropellant composition.

It has been established that certain physical properties are desired inrocket propellant compositions of the JATO, ICBM, and IRBM types. At thepresent time, it is believed that the propellant composition should havean elongation of at least about percent and a tensile strength of atleast about 125 p'.s.i. It also appears desirable to have a modulus aslow as 1000 although this iigure can range up to a few thousand.

I have discovered that good propellant compositions can be made using arubbery binder of the type exemplified by a rubbery copolymer of1,3-butadiene and 2- methyl-S-vinylpyridine, a solid inorganic oxidizingsalt, and, the new ingredient, a chlorinated paraflin Wax. The exastbasis upon which the chlorinated wax improves the composition is notknown but, in view of the work reported herein, it is apparent thatseveral advantages are obtained. Products can be made which cure rapidlyand show substantially no change in aging at elevated temperatures. Therecipes shown simplify production in that the number of ingredientsinvolved is reduced. A further advantage is that it is possible toprovide a sulfur-free propellant unit.

The following are objects of our invention.

An object of my invention is to provide new propellant compositions. Afurther object of my invention is to provide propellant compositionshaving especially desirable physical properties. A further object of myinvention is to provide a sulfur-free propellant composition. A furtherobject of my invention is to provide a new and improved method ofpreparing propellant compositions.

Other objects and advantages of my invention will become apparent to oneskilled in the art upon reading the accompanying disclosure.

Broadly, my invention is based upon the discovery that a good propellantcomposition is obtained when a chlorinated paraflin wax is incorporatedwith a solid inorganic oxidizing salt in a rubbery binder, said rubberybinder comprising a polymer of a conjugated diene and a compound ofpyridine and quinoline series containing a substituent where R isselected from the group consisting of hydrogen and methyl.

The chlorinated paraifins used in my invention are thosejcontaining 25to 70 weight percent of chlorine and they are used in amounts rangingfrom 10 to 50 parts by weight per 100 parts of rubbery binder. The

' Patented Sept. 13, 1960 chlorinated parafiins are commerciallyavailable, representative types being Cerechlor, Paroil 143, Paroil 163and Paroil 173, Clorafin, Chlorowax LV, Chlorowax 40, Chlorowax 50 andChlorowax 70. The chlorinated paraflins are frequently considered asrepresenting three different classes. The materials with low chlorinecontent, say 25 to 30 weight percent, are considered the low chlorinecontaining members; those containing 40 to 55 percent chlorine themiddle group; and paraflins containing around weight percent chlorine asthe high chlorine content parafiins. The materials range from liquidmaterials through resinous materials, the materials becoming harder asthe chlorine content is increased. A method for producing thesematerials is disclosed in Hardie et a1. 2,130,952 (1938).

The chlorinated parafr'ins used in the Work reported in this disclosureincluded Chlorowax 40 and Chlorowax 70. The first of these materials isa clear, almost colorless liquid material cont-aining approximately 40percent combined chlorine by weight which has a specific gravity ofabout 1.15 and a viscosity of 20 to 25 poises at 25 C. Chlorowax 70 is acream-colored, powdered, resinous material with a specific gravity of1.6 to 1.7 and a melting point of to C. The chlorine con tent isapproximately 70 Weight percent.

As those skilled in the art will understand, the conjugated dienes whichcan be employed are, in addition to butadiene, those which contain from4 to 6, inclusive, carbon atoms per molecule and include 1,3-butadiene,isoprene (Z-methyl-1,3-butadiene), piperylene, 2-methyl- 1,3-pentadiene,2,3-dimethyl-1,3-butadiene, and others. Mixtures of conjugated dienescan be used.

The polymen'zable heterocyclic nitrogen bases which are applicable inour invention are those of the pyridine and quinoline series which arecopolymerizable with a conjugated diene and contain one and only onesubstituent wherein R is either hydrogen or a methyl group. That is, thesubstituent is either a vinyl or an alpha-methylvinyl (isopropenyl)group. Of these compounds, the pyridine derivatives are of the greatestinterest commercially at present. Various substituted derivatives arealso applicable but the total number of carbon atoms in the nuclearsubstituted groups, such as alkyl groups, in addition to the vinyl oralpha-methylvinyl group, should not be greater than 12 because thepolymerization rate decreases somewhat with increasing size of the alkylgroup. Compounds where, the alkyl r substituents are methyl and/or ethylare available commerciall-y.

These heterocyclic nitrogen bases have the formula 0 where R is selectedfrom the group consisting of hydroaryl, and combinations of these groupssuch as haloalkyl, alkylaryl, hydroxyaryl, and the like; one and onlyone of said groups being selected from the group consisting of vinyl andalpha-methylvinyl; and the total number of carbon atoms in the nuclearsubstituted groups in addition to the vinyl or alpha-methylvinyl group,being not greater than 12. Examples of such compounds are2-vinylpyridine; 2-vinyl S-ethylpyridine; 2-methyl-5-vinylpyridine;4-vinylpyridine; 2,3,4-trimethyl--vinylpyridine;3,4,5,6-tetramethyl-2-vin ylpyridine; 3-et-hyl5-vinylpyridine;2,6-diethyl-4-vinylpyridine; 2-isopropyl-4-nonyl-5-vinylpyridine;Z-methyl- 5 undecyl 3 vinylpyridine; 2,4 dimethyl 5,6- dipentyl 3vinylpyridine; 2 decyl 5 (alpha methylvinyDpyridine;2-vinyl-3-methyl-5-ethylpyridine; 2- methoxy-4 chloro-6-vinylpyridine;3-vinyl-5-ethoxyp-yridine; 2 vinyl 4,5 dichloropyridine; 2 (alphamethylvinyl) 4 hydroxyl 6 cyanopyridine; 2 vinyl- 4 phenoxy 5methylpyridine; 2 cyano 5 7 (alpharnethylvinyl)pyridine; 3 vinyl 5phenylpyridine; 2- (para methylphenyl) 3 vinyl 4 methylpyridine; 3 vinyl5 (hydroxyphenyl) pyridine; 2 vinylquinoline; 2 vinyl 4 ethylquinoline;3 vinyl 6,7- di n propylquinoline; 2 methyl 4 nonyl 6 vinylquinoline; 4(alpha methylvinyl) S dodecylquinoline; 3 vinylisoq-uinoline; 1,6dimethyl 3 vinylisoquinoline; 2 vinyl 4 benzylquinoline; 3 vinyl- 5chloroethylquinoline; 3 vinyl 5,6 dichloroisoquinoline; 2 vinyl 6 ethoxy7 methylquinoline; 3-vinyl-6-hydroxymethylisoquinoline; and the like.Mixtures can be used.

The copolymers are prepared by polymerizing a major amount of the dienewith a minor amount of the heterocyclic nitrogen base by any suitablemethod. Preferably, the ultimate product has a Mooney viscosity (ML-4)of 10 to 40 although higher Mooney polymers are frequently made and thenmixed with extender oils.

In my invention, the usual pigments, fillers, reinforcing agents,.andantioxidants commonly used in rubbery compositions can be employed. Theusual solid inorganic oxidizing agents are used, probably the best knownthereof being ammonium nitrate and ammonium perchlorate, although agreat many others, potassium nitrate, etc. are known and the particularoxidant does not constitute a feature of the present invention.Obviously, mixtures of oxidants can be used.

Based upon 100 parts by weight of the binder, suitable propellants aremade using the following recipe:

Parts by weight The mixing procedure for the compositions of the presentinvention was one in which a solvent was employed, this representing animprovement over prior mixing procedure wherein the dry ingredients areincorporated in the binder by a dry mixingprocedure such as a roll millor a Banbury mixer. In the present work the rubber and black masterbatch was milled for a short time and then dissolved in a solvent.Solution of the polymer can be carried out in any type of mixer whichprovides rapid agitation and comminution of the rubbery material. Thebest dispersions are made when sufiicient solvent is used to provide amixture containing approximately 30 weight percent of binder in thesolvent. Immediately prior to the addition of other ingredients, it isconvenient to determine the solid content by oven drying a small sampleof the material. The 'binder solvent mixture is then transferred to amixer equipped with dispersion blades, such as a Baker-Perkins mixer. Asthe additional ingredients are added, cooling is usually required inorder. to prevent excessive temperature rise 4 and loss of solvent priorto obtaining a good dispersion. The next step is to add all of the otherbinder ingredients. Since the quantity of these -materials is small ashort mixing time of 1 to 5 minutes is frequently satisfactory. Finally,the solid inorganic oxidizing salt is added and mixing is continueduntil a uniform mixture is obtained. Due to the large quantity of salt,a mixing time of 30 to 120 minutes or more is required. The solvent isthen removed and this is preferably done by raising the temperature andapplying a vacuum. The temperature should be in the neighborhood of theboiling point of the solvent under the conditions of removal. The time,

of removal, of course, varies greatly depending upon the physicalconditions but, usually, a time of 20 to 120 minutes will besatisfactory.

Following the additionof the oxidant the system is adaptable to remotecontrol and I have found that infra red analysis of the off-gas from themixture provides a convenient method for determining when all of the solvent is removed. A large variety of solvents can be used, the onlyrequirement being that it be capable of dissolving the rubbery binderand non-reactive with the binder and the rest of the components in thepropellant composition. Normal hexane wasthe solvent used inthe workreported in the example of this application and other hydrocarbons suchas pentane, cyclohexane, isooctane, etc. can be used. Halogenatedhydrocarbons are also suitable as well as ethers, ketones, etc. Mixturesof solvent materials can be used. The choice of solvent will frequentlybe determined by the ability of the apparatus used to maintain suitabletemperatures. During the mixing, considerable heat is evolved andcooling is required. After the mixing, the mixture is warmed to permitremoval of the solvent. The worker in the field will have littledifliculty in choosing a solvent which will not be excessively volatileat the temperature of mixing and yet will be easily removed at the endof the mixing operation.

The followingexample illustrates my invention but the invention shouldnot be unduly limited thereby:

Example I A butadiene/Z-niethyl-S-vinylpyridine copolymer was preparedby emulsion polymerization at 41 F. using a recipe of the following type1,3-butadiene Potassium pyrophosphate 0.253 Para-menthane hydroperoxide0.1

A series ofruns was made to an average conversion of 85.9 percent, theproducts blended, the resulting rubher having a Mooney viscosity (ML-4)of 22.4. As a shortstop, 0.1 part of potassiumdimethyldithiocarbamatewas used and 1.76 percent by weight, baseduponthe rubber, of phenol-beta-naphthylamine was added as anantioxidant.

The latex was master batched with 22.5 parts by weight of carbon black(Philblack A) per parts of rubber.

Portions of this master batch were incorporated in a. variety of recipesas set forth in the following table. Itwill be noted that the, first tworecipes serve as controls,

I a sulfur cure being used in each. The last two recipes. disclosepropellants prepared using the chlorinated paraffins of the presentinvention. w

Sulfur Cure I Sulfur Cure II Chlorowax-70 Cure Chlorowax-40 Cure Phr Wt.Phr Wt. Phr Wt. Phr Wt.

Percent Percent Percent Percent 100. 10. 75 100. 0 10. 49 100. 0 9. 06100. 0 9. 06 22. 2. 42 22. 5 2. 36 22. 5 2. 04 22. 5 2. 04 10. 0 1. 0310. 0 1. 05 10. 0 0. 91 10. 0 0. 91 3. 0 0. 32 3.0 0. 31, 3.0 0. 27 3.00. 27 3.0 0. 32 Ur. 2. 5 0. 26 Methyl Tuads 1.0 0.10 Santueure 5 1.0 0.11 Stearic Acid 1. 0 0. Zinc Oxide 3.0 0. 31 Chlorowax-70 30. 0 2. 72Chlorowax-40 30. 0 2. 72 Binder Total 139. 5 15. 148. 0 15.00 165. 515.00 165. 5 15.00 Ammonium Perchlorate- 70. 00 70.00 70.00 70. 00Ammonium Nitrate"--- 15. 15.00 15. 00 15. 00 Propellant TotaL.-. 100. 00100. 00 100.00 100. 00

1 An aromatic oil used as rubber extender.

Morpholine disulfide. 4 Tetremethyl thluramdisulfide. N-cyolol1exyl-2-benzothiazylsulfenamide.

Each of these compositions was made by a particular procedure. At thestart, 600 grams of the butadiene/Z- methyl-S-vinylpyridine polymercontaining the carbon black was milled for 3 minutes with the water onthe rolls set at 120 F. After this milling, the polymer was dissolved innormal hexane using a Model l-VG Cowles Dissolver, a variable speedchurn utilizing a combination cutter-impeller to facilitate solution.One-half gallon of normal hexane was used for the binder which was cutinto small pieces in order to facilitate solution. During thedissolving, the copolymer was cleaned from the sides of the containerand the impeller every fifteen minutes and additional normal hexane wasadded to maintain a solution of approximately 30 percent by weightrubber solids. The operating speed of the dissolver was maintained inthe range of 2900 to 3000 rpm. approximately 2% hours being required toobtain a smooth solution. The solids content of the mixture at thispoint circulating through-the bowl at approximately F. All of theingredients were added except for the am monium perchlorate and ammoniumnitrate and the resulting mixture was mixed for two minutes. Thereafterthe oxidants were added and mixing was continued for sixty minutes. Atthis point, while continuing mixing, the temperature was raised and allof the solvent removed. This was accomplished by raising the temperatureof the water supplied to the mixer to about 140 F., the temperature ofthe mixer rising to the boiling point of the solvent. tem to acceleratesolvent removal which took approximately 35 minutes. Infrared analysisof the off-gas from the mixer indicates degree of removal of thesolvent.

Test specimens were prepared in order to determine elongation, tensile,modulus, and ignition and ballistic properties on each of thecompositions. The results of these tests are set for-thin Table II:

Sulfur Cure I Sulfur Cure II Ohloaowax-7O Chlorowax-40 ure Cure PhysicalProperties St E 6 St E Cure at 190 F.:

72 hours Oven age at 190 F.:

1 week 2 weeks 4 weeks 5 sec. @[5 min. Impact Sensitivity. Density #/in.

e04 F/480 F. 52 lnJlb. 0.0607.

1 Sample Overcnred.

was determined by oven drying a 4-6 gram portion for one hour at F. andadditional solvent was added as needed to maintain the 30 percentsolution. The mixture was then transferred to a Baker-Perkins mixerequipped with dispersion blades and the additional ingredients wereadded while maintaining cooling water Examination of the data of thistable shows that excellent properties can be obtained using thecompositions of the present invention. The run using Chlorowax 70 isparticularly outstanding because of the excellent tensile valuesobtained and the modulus in the desired range. Another outstandingfeature is the small change in these A vacuum was applied to the sys-,

7 physical properties regardless of the time of cure. The compositionusing the Chlorowax 40 is also very good, although longer curing timesare required. Both compositions are superior to the control compositionsusing ,the sulfur cure. The ignition and ballistic properties of bothcompositions containing Chlorowax are good. The compositions are notpressure sensitive, and provide :propellants of higher density, thisbeing an improvement.

invention without departing from the scope thereof, it is to beunderstood that all matter herein set .forth is to be interpreted asillustrative and -not'as unduly the invention.

I claim:

1. A rocket propellant composition consisting essentially of a rubberybinder, said :binder being a rubbery copolymer of 1,3-butadiene and2-methyl-5-vinylpyridine and, based upon 100 parts by weight of saidrubbery binder, to 60 parts of a filler, 0 to 20 parts of a plasticizer,0 to 3 parts of an antioxidant, 100 to 900 parts of a solid inorganicoxidizing salt, and to '50 parts 'of'a chlorinated parafiin, saidchlorinated paraffin being a liquid to resinous material containing 25to 70 weight percent of chlorine and having a specific gravity in therange of 1.15 to 1.7.

2. A rocket propellant composition consisting essentially of a rubberybinder, said binder being a rubbery polymer of a conjugated diene of 4.to 6 carbon atoms and a compound of the pyridine and quinoline seriescontaining a substituent where R is selected from the group consistingof hydrogen and methyl and, based upon 100 parts by weight of saidrubbery binder, 0 to 60 parts of .a filler, 0 to parts of a plasticizer,0 to 3 parts of an anti-oxidant, 100 .to 900 parts of a solid inorganicoxidizing salt, and 10 to 50 parts of a chlorinated parafiin, saidchlorinated paraffin being a liquid to resinous material containing to70 weight percent of chlorine and having a specific gravity in the rangeof 1.15 to 1.7.

3. The composition of claim 2 wherein said polymer is a polymer of1,3-butadiene and 2,5-vinylpyridine.

4. The composition of claim 2 wherein said polymer is a polymer of1,3-butadiene and 2-vinylpyridine.

5. A rocket propellant composition consisting essentially of thefollowing ingredients:

Parts by weight Butadiene/2-methyl-5-vinylpyridine copolymer 9.06 Carbonblack 2.04 Plasticizer 0.91 Antioxidant 0.27 Chlorinated parafiin 2.72Ammonium perchlorate 70.00 Ammonium nitrate 15.00

having a specific gravity in the range of 1.15 to 1.7.

6. The method of preparing arocket propellant com- I prising milling arubbety binder, said binder comprising a rubbery copolymer of1,3-butadiene and Z-methyl-S- vinylpyridine, dissolving said binder innormal hexane,

the :amount of said normal :hexane being sufiicient to As many possibleembodiments can be. made of this elem provide a rubber content ofapproximately 30 percent,

adding with agitation 'the rest of the propellant com-j 'ponents, saidcomponents including 10 to 50 parts by -weight of a chlorinated paraffinper 100 parts of said rubbery binder, said chlorinated paralfin being aliquid to resinous material containing 25 to weight percent of chlorineand having a specific gravity in the range of 1.15 to 1.7, and raisingthe temperature of the mixture to remove the normal hexane.

7. 'The method of preparing a rocket propellant comprising milling arubbery binder, said binder comprising a rubbery polymer of a conjugateddiene of 4 to 6 carbon atoms and a compound of the pyridine andquinoline series containing a substituent where R is selected from thegroup consisting of hydrogen and methyl, dissolving the binder in an organic solvent, said solvent being capable ofdissolving the binder butnon-reactive with said binder, the amount of said solvent beingsufficient to provide a rubber content of approximately 30 percent,adding the rest of the propellant components, said components including,based upon parts by weight of binder, 10 to 50 parts ofa chlorinatedparaflin, said chlorinated paraffin being a liquid to resinous materialcontaining 25 to 70 weight percent of chlorine and having a specificgravity in the range of 1.15 to 1.7.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Chem. and Eng. News, Oct. 7, 1957, pages 62-63.

1. A ROCKET PROPELLANT COMPOSITION CONSISTING ESSENTIALLY OF A RUBBERBINDER, SAID BINDER BEING A RUBBER COPOLYMER OF 1,3-BUTADIENE AND2-METHYL-5-VINYLPYRIDINE AND, BASED UPON 100 PARTS BY WEIGHT OF SAIDRUBBERY BINDER, 0 TO 60 PARTS OF A FILLER, 0 TO 20 PARTS OF APLASTICIZER, 0 TO 3 PARTS OF AN ANTIOXIDANT, 100 TO 900 PARTS OF A SOLIDINORGANIC OXIDIZING SALT, AND 10 TO 50 PARTS OF A CHLORINATED PARAFFIN,SAID CHLORINATED PARAFFIN BEING A LIQUID TO RESINOUS MATERIAL CONTAINING25 TO 70 WEIGHT PERCENT OF CHLORINE AND HAVING A SPECIFIC GRAVITY IN THERANGE OF 1.15 TO 1.7.